first debate here in denver. >> governor romney has shown himself to be a very good debater. >> pelley: do you think the debates are make or break for you? plus, nancy cordes, jan john dickerson on what could be a turning point in the race. bombs are turning one of the world's most historic cities into rubble-- at least 40 dead today. clarissa ward on who's behind it. most americans take supplements, but do they work? dr. jon lapook has the results of a new investigation. and anthony mason with unforgettable debate moments. >> there you go again. >> who am i? >> you're no jack kennedy. >> pelley: so give a listen. >> i'm all ears. captioning sponsored by cbs this is the "cbs evening news" with scott pelley reporting tonight from denver. >> pelley: good evening, president obama and mitt romney meet here tonight on the stage behind me at the university of denver for their very first debate. the stakes are high because 34 days before the election this race is still up for grabs. the latest poll of likely voters by the "wall street journal" shows the president with a three-point lead over